The present invention relates particularly to direct extrusion of a hollow elongated workpiece such as metal tube or tubing, and particularly to a method and apparatus for sealing the trailing end thereof to prevent water from entering the inside of the tubing while being completely submerged in water after the extruding process.
In present day tube extrusion practice it is becoming highly desirable to subject extruded non-ferrous tubing, such as copper tubing, to water treatment since the water temperatures can be easily maintained to accelerate the cooling process to keep grain growth and oxidation of the extruded product to a minimum.
However, the entrance of water into the inside diameter of the tubing creates several problems, such as drainage and safety problems since the water drains onto the plant floor. In addition to this, employees handling the tubing during subsequent operations are continually subjected to the draining water. Also, subsequent drawing operations of the tubing are hampered by the presence of water and saw chips inside the tubing.
In order to overcome these hazards and disadvantages, it has become common practice to close both the leading and trailing ends of the tubing prior to the water treatment.
One common method practiced in extruders using a floating constant diameter mandrel, is to pierce, at the beginning of the extrusion stroke, a billet to within a short distance of the die to first produce a short section of solid rod. The mandrel is then inserted into the die for the completing of the extrusion process; however, shortly before the end of the extrusion stroke the mandrel is retracted out of the tube and die and again a short piece of rod is extruded. Since the mandrel has a constant diameter and the dummy block has a hole slightly greater than the outer diameter of the mandrel a seal is maintained between the outer diameter of the mandrel and the hole in the dummy block, thereby enabling the ram to extrude this short piece of rod.
Problems arise, however, when an arrested mandrel is used. Such mandrels are stepped having a large shank and a reduced diameter tip for extruding small tubing. When the stepped mandrel is withdrawn from the die and tube, the tip enters the dummy block hole. Under this condition when the main ram is brought forward to close the trailing end of the tube it is quite likely that the metal will extrude backwards into the hole of the dummy block as well as forward through the die. Even with precise dimensioning of the mandrel tip, and a very fine manipulation of the mandrel and ram it is virtually impossible to overcome this occurrence.
It is, therefore, an object of the present invention to overcome the above disadvantages of the prior method of extrusion particularly using a stepped mandrel by providing a method and apparatus for closing the trailing end of the tubing just after the end of the extrusion stroke.
It is another object of the present invention to provide a method which can be practiced in conjunction with an apparatus which can be used on original equipment or added to existing presses.
More particularly, an object of the present invention is to provide a method and apparatus for crimping the trailing end of a tubing prior to the trailing end being submerged in water.
It is a still further object of the present invention to provide a method used in combination with a machine for producing a hollow elongated workpiece wherein in the production of the workpiece the leading end thereof has a closed end, the steps comprising: completing the remainder of the production of the workpiece including the trailing end thereof, and before the hollow trailing end portion is exposed, deforming a hollow portion of the workpiece inward of the trailing end in a manner to close off the trailing end.
A still further object of the present invention is to provide an apparatus used in combination with a machine for producing a hollow elongated workpiece, wherein in the production of the workpiece the leading end thereof has a closed end, an apparatus comprising: means for operating said machine to produce the remainder of the workpiece including the trailing end thereof, and means operable before the hollow trailing end of the workpiece is exposed for deforming a hollow portion of the workpiece inward of the trailing end in a manner to close off the trailing end.